Shouldn't really open another post on this, but I'll be quick.
OK. In your minds, take the disc off, take the two shoes and lay them inside the drum. Oooh, they fit perfectly. Look at the 100% contact that the friction material makes with the shiny metal. Now, the issue is that when you reassemble the whole thing, the shoes don't sit like that. Well they can't touch can they or the brake would be on. So they pivot a little so that the friction material pulls away from the curve of the drum. Now where the thing is poor, is that unless the pivot point for the arc is in exactly the right place, the shoes won't touch along their full length. What in fact happens is that they touch a little bit typically at the top. The idea of the mechanism is the the shoes should actually pivot and be pushed apart at the top by the dog bone. But as we know they don't any more at least. So what happens is that you get a great feel on the handbrake lever - really solid, but no braking effect. That's because there's only a smidge of the material in contact with the drum and that's not enough to stop the wheel.